1. Field of the Invention
The present invention relates to twin clutch type speed-change apparatuses and, in particular, to a twin clutch type speed-change apparatus that reduces shift shock by providing a step on dog teeth provided on a speed-change gear sliding on a shaft.
2. Description of Background Art
Japanese Patent Laid-Open No. 2007-100739 discloses a multi-step transmission having a plurality of speed-change gear pairs configured such that shifting operation is executed by allowing shift forks parallel sliding on a main shaft and a countershaft to drive speed-change gears and sleeves slidable on the main shaft and the countershaft.
In particular, this document discloses a twin clutch type speed-change apparatus in which a main shaft is of a double structure consisting of an inner tube and an outer tube and which is provided with a first clutch and a second clutch that transmit a rotational drive force to the inner main shaft and the outer main shaft, respectively. In addition, this speed-change apparatus is configured to be provided with sleeves and speed-change gears axially driven by shift forks and to allow a dog clutch composed of a dog tooth and a dog hole to transmit an axial drive force to a gear coaxially adjacent to the speed-change gear.
The twin clutch type speed-change apparatus as disclosed in Japanese Patent Laid-Open No. 2007-100739 can execute shifting operation by switching the engaging state between the first clutch and the second clutch with a predetermined dog clutch remaining engaged. In this speed-change apparatus, a rotational drive force applied to the dog clutch remaining engaged during the shifting operation is changed, whereby the abutment surface between the dog tooth and the dog hole is changed to another abutment surface. There is a possibility that a flapping sound and/or shock may occur at that time.